• 한국소음진동공학회논문집
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• 제24권4호
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• pp.324-331
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• 2014

The sensor configuration of the magnetostrictive guided wave system can be described as a single continuous transducing element which makes it difficult to separate the individual modes from the reflected signal. In this work we develop the mode decomposition technique employing chirplet transform based on the maximum likelihood estimation, which is able to separate the individual modes from dispersive and multimodal waveform measured with the magnetostrictive sensor, and estimate the time-frequency centers and individual energies of the reflection, which would be used to locate and characterize defects. Simulation results on a carbon steel pipe are presented, which show the accurate mode separation and more discernible time-frequency representation could become enabled using the proposed technique.

• 한국소음진동공학회논문집
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• 제25권6호
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• pp.399-405
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• 2015

In this work we use the mode decomposition technique employing chirplet transform, which is able to separate the individual modes from dispersive and multimodal waveform measured with the magnetostrictive sensor. The mode decomposition technique is also used to estimate the time-frequency centers and individual energies of the reflection, which would be used to locate and characterize axial defects. The arrival times of the separated modes are calculated and the axial defect lengths can be evaluated by using the estimated arrival time. Results from an experiment on a carbon steel pipe are presented and it is shown that the accurate and quantitative defect characterization could become enabled using the proposed technique.

• 한국압력기기공학회 논문집
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• 제17권1호
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• pp.56-63
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• 2021

The feedwater ring is an assembly in steam generator internal piping, which distributes feedwater into the secondary side of the steam generator. It consists of an assembly of carbon steel piping, pipe fittings and J-nozzles which are inserted into the top of the feedwater ring and welded to the diameter of the ring. The feedwater ring at the attachment region of the J-nozzle may be susceptible to flow accelerated corrosion (FAC) due to flow turbulence which increases local fluid velocities. If a J-nozzle becomes a loose part, it can cause damage to tubing near the tube sheet. In this paper, the structural stress analysis for a wall thinned feedwater ring and integrity evaluations under assumed loading conditions are carried out in compliance with ASME B&PV SecIII, NB-3200.

• Journal of Microbiology and Biotechnology
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• 제14권6호
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• pp.1114-1119
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• 2004

The biofilms on pipe walls in water distribution systems are of interest since they can lead to chlorine demand, coliform growth, pipe corrosion, and water taste and odor problems. As such, the study described in this paper is part of an AWWARF and Tampa Bay Water tailored collaboration project to determine the effect of blending different source waters on the water quality in various distribution systems. The project was based on 18 independent pilot distribution systems (PDS), each being fed by a different water blend (7 finished waters blended in different proportions). The source waters compared were groundwater, surface water, and brackish water, which were treated in a variety of pilot distribution systems, including reverse osmosis (RO) (desalination), both membrane and chemical softening, and ozonation-biological activated carbon (BAC), resulting in a total of 7 different finished waters. The observations from this study consistently demonstrated that unlined ductile iron was more heavily colonized by a biomass than galvanized steel, lined ductile iron, and PVC (in that order) and that the fixed biomass accumulation was more influenced by the nature of the supporting material than by the water quality (including the secondary residual levels). However, although the bulk liquid water cultivable bacterial counts (i.e. heterotrophic plate counts or HPCs) did not increase with a greater biofilm accumulation, the results also suggested that high HPCs corresponded to a low disinfectant residual more than a high biofilm inventory. Furthermore, temperature was found to affect the biofilms, plus the AOC was important when the residual was between 0.6 and 2.0 mg $Cl_2/l$. An additional aspect of the current study was that the potential of the exoproteolytic activity (PEPA) technique was used along with a traditional so-called destructive technique in which the biofilm was scrapped off the coupon surface, resuspended, and cultivated on an R2A agar. Both techniques indicated similar trends and relative comparisons among the PDSs, yet the culturable biofilm values for the traditional method were several orders of magnitude lower than the PEPA values.

• 상하수도학회지
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• 제20권4호
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• pp.545-558
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• 2006

The current conditions of large water mains are evaluated by deteriorations and the causes of deterioration are investigated through visual assessments in the field, mechanical tests and analysis of chemical compositions in laboratory for each pipe material, unlined cast iron pipes (CIPs), ductile iron pipes (DCIPs) and steel pipes (SPs) Tubercles and scales from internal and external corrosion of unlined cast iron pipes were identified as the causes of functional performance limitations in large water mains. It is investigated that main causes of internal and external corrosion of water pipes are from lots of depositions of organic and inorganic substances on pipe surface, concentrated pitting, and uniform corrosion by local or global exfoliation or detachment of lining and coatings of DCIPs and SPs. Internal and external corrosion depths of CIPs were higher than those of DCIPs and SPs. Consequently, total corrosion rate summed internal and external corrosion rates of CIPs also were shown to be higher than those of DCIPs and SPs. The failure time from hole generation of CIPs by total corrosion rate was predicted to be taken sixteen years, and DCIPs and SPs were twenty-six years and one hundred and fifty three years. And longitudinal deflection of investigated water mains were not happened and mechanical strengths such as tensile strength, elongation, and hardness also were mostly suited to Korea Standards. It was thought that the weakness of tensile strength of one sample(S-11) was, however, due to higher carbon contents(%) in CIPs. Pipe deterioration score of S-46 was 55.2 and was preferentially assessed to be rehabilitated.

• 한국화재소방학회논문지
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• 제34권4호
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• pp.69-77
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• 2020

최근 건축물의 대형화, 복잡화로 인하여 화재 발생 시 그 피해가 증가하고 있어 수계소화설비에서 스프링클러설비의 중요성이 확대되고 있다. 소방용 배관재로는 탄소강관(일반배관용·압력배관용), CPVC관, 동관, 스테인리스강관 등이 있으며, 소방용 배관으로 널리 사용되고 있는 강관배관 및 CPVC관에 대하여 배관의 노화를 고려한 부식계수 적용 시 말단헤드에서의 유량과 압력을 분석하기 위해 PIPENET 수리계산프로그램을 사용하여 수계시스템의 신뢰성을 분석하였다. 강관을 적용하였을 경우 배관 구경이 동일한 조건에서 20년경과(C값 90)후 지하 1층에 설치된 펌프에서의 정격유량은 10% 이상 감소하였으며, 말단헤드에서의 압력과 유량은 각각 30%, 16.5% 이상 감소하여 소방시설의 신뢰성 확보에 문제가 있는 것으로 확인되었다. 또한 30년(C값 80) 경과 시 펌프에서의 정격유량은 15% 이상 감소하였으며, 말단헤드에서의 압력과 유량은 각각 42%, 24% 이상 감소하는 것으로 결과 값이 도출되었다.

• Bulletin of the Korean Chemical Society
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• 제32권12호
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• pp.4270-4274
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• 2011

A method is proposed for determining chromium content in the carbon steel pipes of a nuclear power plant (NPP) to evaluate wall thinning caused by flow-accelerated corrosion (FAC). A flat file was used to obtain filings samples. To assess sampling quality, a disk form of SRM 1227 was ground with the flat file, and the amount of Cr in the filings was determined by ICP-AES. The content of chromium in the filings of SRM 1227 was estimated as six times higher than the certified value due to the contamination of chromium in the file. To eliminate chromium contamination from the file, it was coated with WC-12Co using high-velocity oxygen-fuel (HVOF) spraying systems. After obtaining filings samples using the coated file, Cr content in four types of disk-form SRMs was determined by ICP-AES. The recoveries of Cr in the disk-form SRMs were in the range of 95.4-102.6%, with relative standard deviations from 0.43 to 3.0%. The Cr contents in the filings collected from the used outlet headers of the nuclear power plants using the flat file coated were in the range of 0.11-0.19%.

• 대한기계학회논문집B
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• 제35권10호
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• pp.1105-1110
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• 2011

유동가속부식(FAC)은 가장 잘 알려진 탄소강 배관 손상 메커니즘으로 현재 국내 전 원전에서는 유동가속부식으로 인한 감육현상을 관리할 수 있는 체계적인 방안이 수립되어 있다. 그러나, 발전소 배관은 다양한 침식손상 메커니즘에 의해 여전히 손상을 받고 있다. 대표적인 침식 메커니즘은 캐비테이션, 액적충돌침식(LDIE), 플래싱, 고체입자침식(SPE)이다. 본 논문에서 기술하는 액적충돌침식 은 손상예측이 어렵고, 관리를 위한 체계적인 방안도 수립되어 있지 않다. 본 논문에서는 실제 발전소 현장에서 발생한 사례를 바탕으로 기존에 개발된 예측 모델과 실험을 통해 얻어진 상관식을 비교하여 액적충돌침식으로 인한 손상을 평가할 수 있는 방법을 제시하였다.

• 한국산업융합학회 논문집
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• 제7권3호
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• pp.259-263
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• 2004

In the manufacture progress of LCD or semiconductor, there are used many kinds of gas like erosion gas, dilution gas, toxic gas as a progress which used these gas there are required high puritize to increase accumulation rate of semiconductor or LCD materials work progress of semiconductor or LCD it demand many things like the material which could minimize metallic dust that could be occured by reaction between gas and transfer pipe laying material, illumination of the surface, emition of the gas, metal liquation, welding etc also demand quality geting stricted. Material-Low-sulfur-contend (0.007-0010), vacuum-arc-remelt(VAR), seamless, high-purity tubing material is recommend for enhance welding lower surface defect density All wetted stainless steel surface must be 316LSS elecrto polishinged with ${\leq}0.254{\mu}m$($10.0{\mu}in$) Ra average surface finish, $Cr/Fe{\geq}1.1$ and $Cr_2O_3$ thickness ${\geq}25{\AA}$ From the AES analytical the oxide layer thickness (23.5~36 angstroms silicon dioxide equivalent) and chromum to iron ratios is similar to those generally found on electropolished stainless steel., molybdenum and silicon contaminants ; elements characteristic of stainless steel (iron, nickel and chromium); and oxygen were found on the surface Phosphorus and nitrogen are common contaminants from the electropolish and passivation steps.

• 한국재난정보학회 논문집
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• 제12권1호
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• pp.1-9
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• 2016

국부적인 두께감소 문제에 대하여 직관부위를 대상으로 한 건전성 평가는 잘 알려져 있으나 엘보우를 대상으로 한 건전성 평가는 최근에 원자력 분야에서는 많은 연구가 이루어지고 있으나 석유화학 플랜트에서 이용되는 건전성 평가 지침서 중 하나인 API579 코드에는 아직 없는 실정이다. 이에 본 연구에서는 엘보우를 대상으로 엘보우의 외부(extrados)와 내부(intrados)에 두께 감소가 있다고 가정한 후 유한요소해석법을 이용하여 두께감소된 엘부우의 건전성평가 해석을 수행하였다. 본 해석 결과는 석유화학 플랜트에서 이용되는 엘보우의 건전성 평가에 이용될 수 있음을 보여주었다.